1. Field of the Invention
This invention relates generally to microwave systems employing passive components, and more particularly, to microwave systems in which the amplitude and phase of the output signals is varied utilizing an electromechanical, variable, microwave power divider.
2. Description of the Prior Art
At the present state of the art, the solutions employed for the realization of a wave-guide variable power divider were generally based on two possible classes of configurations.
The first class of configurations employed two hybrid circuits and two complimentary variable phase shifters. The first hybrid circuit, with orthogonal output gates ("T" type), generated, from the input signal, two signals of equal amplitude at its outputs, which signals were subjected to a relative phase shift by the variable phase shifters. The second circuit then recombined these signals, so that one of the two outputs gave the sum of the two signals and the other the difference between the two signals. In this manner two signals were generated, the amplitudes thereof depending upon on the electric phase-shifting angle introduced by the variable phase shifters, according to two sine functions in quadrature to each other. The critical feature of this solution resides in the fact that the actuating element for power regulation was the electrical phase-shift angle, which by nature depends on the frequency, and this fact inevitably limited the variable power divider's inband performance. The second class of variable power divider configurations utilized a variable polarization rotator between two linear polarization separators known as "OMT" (Ortho Mode Transducers). Since the output gates were not aligned, dividers of this type could not be easily integrated into more complex planar networks.
The solutions regarding the first class of configurations have several disadvantages. For example, the first input hybrid circuit is of the "T" type, i.e., with one of the two gates outside the plane containing the device's circuitry development, and therefore it does not allow the planar development of the device. Moreover, the circuitry layout of the proposed components, in the event that the variable phase shifters are constituted by hybrids short-circuited at the output, is generally of the "cross" type, i.e., with the 4 hybrids set out perpendicularly to one another; this makes it impossible to optimize the dimensions and limits the possibility of integrating the device in beam-forming networks. Further, the movable short-circuits made with sliding contacts or small distances in relation to the waveguide containing them, can cause discharge or radio frequency power loss phenomena when high powers are used. Finally, the phase response obtainable from variable phase shifters is closely linked to the scatter from the short-circuited line segment, and this entails considerable amplitude and phase variations in the device's inband output in relation to the central frequency value.
The solutions applying to the second class of configurations have the disadvantage of preventing the integration of the device in more complex planar networks.
It is therefore an object of the present invention to provide an easily integratable, low-loss, broad-band variable power divider which is operable at medium-to-high power levels.
It is also an object of the present invention to provide a circuit configuration in which the output gates of the first input hybrid circuit are disposed in the same plane, thereby permitting a planar construction.
It is a further object of the present invention to provide a circuit configuration which utilizes non-sliding, movable short circuits with resonant cavities, thereby avoiding the problems of discharge or radio frequency power loss experienced by prior art devices at high powers.
It is yet another object of the present invention to provide a circuit which can be integrated into complex planar networks.